1. Field of the Invention
The present invention relates to an electrode device for intracorporeal stimulation of body tissue, in particular for intracardial stimulation of heart tissue of the type having an electrode cable containing a coiled, flexible, insulated first wire running substantially the entire length of the electrode cable, and whose interior forms a channel, with at least one partially conductive electrode head provided on the distal end of the electrode cable, and with a second wire provided in the channel, wire running the entire length of the electrode cable and attached at or near the electrode cable's distal end.
2. Description of the Prior Art
It is of major importance for the electrode cable in an electrode of this type to be sufficiently pliant to enable it to follow the venous pathway during introduction into a patient's heart through a vein without damaging venous walls. For conventional electrodes, the cable is introduced with the aid of a stylet, inserted into the cable's channel, made of a material offering the stiffness which is required for advancing the electrode cable through veins. The stiffness of the electrode cable can be varied, depending on the stylet's diameter and material. At awkward passages in which the electrode cable must be, e.g., bent sharply, the styler is often retracted a little to maximize the pliability of the electrode cable's distal end. (As used herein, "distal" means distal relative to a yet-to-be connected stimulation device, and the "distal end" of the electrode cable is the end which will come into contact with heart tissue. The "proximal end" of the electrode cable is the end which will be connected to the stimulation device.) After the cable has traversed such a passage, the stylet is again advanced to the distal end of the electrode cable so as to advance this end to the atrium or ventricle of the heart until the electrode head presses against heart wall for stimulation of the heart. Introduction of an electrode cable into a vein with the aid of a stylet is therefore not an entirely simple procedure for the surgeon.
An electrode device of the above-mentioned kind is disclosed in U.S. Pat. No. 4,677,990. The end of the second wire is attached to the electrode head. This wire runs the entire length of the channel and is eccentrically arranged between the first wire and the electrode cable's external insulation. When the surgeon pulls on the wire, the distal end of the electrode cable is bent into a J-shape. Introduction of the electrode cable into a patient's heart is performed with the aid of a stylet.
Another similar electrode device is prior art through the German OS 25 16 848. The function of the second wire in this electrode device is to release a spring-loaded anchor provided on the electrode head. The proximal end of the wire also runs through a lateral hole in the proximal end of the electrode cable. As a result of the wire's position inside the electrode cable, the electrode cable bends when the wire is tensioned until the distal end of the electrode cable assumes a J-shape. There is no description in German OS 25 16 848 of the way in which the electrode cable is introduced into the patient's heart.